Telephone-transmitter



w. AND J. BIRRELL. TELEPHONE TRANSMITTER. APPLICATION FILED JUN-E27, 1916- REN EWED JAN. 19, 1920. 1,342,582, Patented June 8, 1920.

ml m5 1, amr e 0/3. flag MK w z J omrs WILLIAM IBIRRELL AND JAMES BIRRELL, OF CHICAGO, ILLINOIS, ASSIGNORS, TO THE.

AUDIBLE TELEPHONE COMPANY, A CORPORATION OF DELAWARE.

TELEPHONE-TRANSMITTER.

Specification of Letters Patent.

Application filed June 27, 1916, Serial No. 106,893. Renewed January 19, E20. Serial No. 352,636.

in the comminuted carbon material is subjected to agitation between two relatively fixed electrodes.

One of the objects of the invention is the provision of a more efficient variable resistance medium through the employment of abody of loose carbon granules disposed between two relatively fixed electrodes adapted to be vibrated in unison upon a diaphragm, said granules being unaffected by compression or decompression of said electrodes.

Another object of the invention is a more perfect transmission of sound'waves to the electric current resistance varying devices through the provision of a loosely housed diaphragm with which both electrodes of said device are rigidly connected, whereby the diaphragm movements completely respondto the sound impacts of the voice unaccompanied by overlaying foreign tones due to distortion or undue molecular strain of ,themetal or material from which the diaphragm is made.

It is an important object of this invention to provide a telephone transmitter with relatively rigid electrodes mounted on a loosely housed diaphragm and adapted.- to vibrate in unison thereby eliminating packing of the granular variable resistancematerialbetween the electrodes.

The'invention consists inthe novel construction of a telephone transmitter described in the following specification, illustrated in the accompanying drawings (in a preferred form), and finally set forth in the appended claims.

In said drawings, Figure-1 is a view in longitudinal section of a telephone transmitter embodying our invention.

Fig. 2 is a view in rear elevation of the same with the back plate partly broken away to expose a portion of the interior mechanism.

Fig.3 is an enlarged fragmentary view of a detail shown in Fig. 1. Referringfto said views, the reference numeral 1 indicates a casing formed with a central threaded aperture with which the mouth-piece 2 is connected. A back plate 3 is secured upon the reverse side of said cas- Manama 8,1920.

ing, as by screws 5, inclosing a diaphragm compartment 6. I

An. unconfined circular diaphragm plate 7 is positioned within said compartment. A rubber insulating ring 8 is engaged about the peripheral edges of saiddiaphragm.

The rubber ring 8 serves to electrically insulate the diaphragm from the casing and also to insulate the diaphragm from any foreign vibrations of the casing.

The diaphragm is formed with a centrally disposed electrode-chamber 10 having a front wall 11. A metalffbutton 12having a carbon electrode 13 secured in intimate electrical contact to its rear face is rigidly connected to said front wall by a screw-stud 15 and nut 16 preferably integral therewith.

Anoppositely disposed electrode 17'is secured in like manner to a button 18 which is connected by screw-stud 20 and nuts 21 to a mica disk 22 which forms the rear. wall of said electrode chamber 10 and is secured at its edges by rivets A metal ring 25 overlays said disk upon which the heads of said rivets bear.

Electrical circuit wires 26 and 27 are reif spect'ively connected by nuts 21 to studs 20 of electrode 17 insulated "from the diaphragm to said insulating disk, and to screwbolt 28 performing the 'oflice of one of rivets 23 through which electrical current may pass through the side and front walls of said electrode chamber, stud 15 to electrode 13.v v

A plurality of felt blocks 30 are indicated as cemented or otherwise secured to backplate 3' to prevent too great displacement of the diaphragm? Said felt blocks also serve to insulate the diaphragm from any foreign vibrations which may be set up inthe casing.

'A quantity of carbon granules fill approximately two-thirds of the space within said chamber 10 and are maintained in loose contact between said electrodes.

Impact of sound waves upon the diaphragm causes the latter to vibrate, and

both electrodes 13' and 17 being secured to thediaphragm with'substantially the same shaken by the aforesaid vibrations in the field between said electrodes, into states of activity of the separate carbon particles 7 seemingly proportionate to the sound waves of the actuating voice, and conveying from one electrode to the other electrical impulses and currentin direct ratio to the quantity of sound affecting the diaphragm.

In transmitters having. electrodes which are movable relative to each other, great diiiiculty is experienced with packing of the granular variable resistance material contained between the electrodes. This packing effect is caused by the settling of the granular material when the electrodes are at the widest point of separation and is often brought about by a sudden jarring of the transmitter or by sucking in the mouthpiece. When a transmitter becomes packed the transmission of speech thereby becomes impossible and the telephone to which it is attached is useless until a new transmitter is provided or the old one repaired. In the design of telephone transmitters adapted to give continuous service under all conditions of operation it is particularly desirable that a .nonpacking type be provided. In our improved form of transmitter, packing of the granular material is eliminated by providing electrodes 'which are relatively rigid and which can not be easily separated. Since the electrodes vibrate in unison and with the granular material there is no danger of packing due to violent vibrations. The variations of resistance afforded by the construction described, wherein the carbon granules are maintained in loose contact unaliected by the pressure of the electrode, is extremely wide and sensitive, carrying equally well and with true quality of tone, a shrill piercing whistle and the lowest notes the human-voice can utter, Also the quality of tone is very perfectly ren dered, the distinctive overtonesand harmonics of voices beingas sensitively accepted and transmitted as the leading notes. 7

Concurrently with the advantages afiorded by our improved form or resistancevarying devices, are those rendered by the provision of a diaphragm loosely housed within the case and free to vibrate under the'sound impacts throughout its whole ex- I tent without creation of discordant tones due to the undue distortion of the metal where the outer edges of the diaphragm are confined.

We are aware-that numerous details of claim is 1. A transmitter including a loosely housed diaphragm, and two parallel electrodes mounted relatively rigid upon said diaphragm. v

2. A transmitter including a loosely housed diaphragm having an electrode chamber in its central portion, electrodes r gidly mounted with respect to each other upon opposite sides of's'aid'chamber, and a 1 quantity of variable resistance granules within said chamber.

3. A transmitter including a loosely housed diaphragm having an electrode chamber partially filled with granular conducting material, and a pair of electrodes,

mounted relatively rigid in said' chamber to avoid compression of said granules.

4. A transmitter comprising a casing, a

diaphragm'loosely housed in said casing, a

pair of parallel relatively rigid electrodes supported from opposite sides of said diaphragm, and a variable resistance medium retained between said electrodes.

5. In a telephone transmitter a diaphragm', an electrode chamber formed centrally therein, an electrode secured in the chamber parallel to the plane of the diaphragm, an insulating cover for the chamber, an electrode inside the chamber parallel to the first mentioned electrode and secured to the cover, and a ring riveted "to the diaphragm for securing the cover in position thereon. I

6. A transmitter "comprising a casing, a diaphragm loosely housed in said casing, non-metallic cushioning means "for insulatingthe diaphragm from the casing, a pair of relatively rigid electrodes supported on the diaphragm, and a'variable resistance medium retained between said electrodes.

7. A transmitter comprising a casing,-a diaphragm loosely housed therein, and a pair of insulated relatively rigid electrodes supported on and inclosed by the diaphragm.

Signed at Seattle Washington, this'QOth day of June, 1916 7 WILLIAM BIRRELL. JAMES BIRRELL.

Witnesses:

E. PETERSON, HORACE BARNES.. 

